1. Field of the Invention
The present invention relates to an antenna apparatus that is mounted on a moving body such as an airplane for microwave communication with a communication satellite or the like, as well as to a waveguide rotary coupler used in such an antenna apparatus.
2. Description of the Related Art
FIG. 10 is a block diagram showing the configuration of a conventional antenna apparatus. In FIG. 10, reference numeral 1 denotes a movable part and reference numeral 2 denotes a fixed part that supports the movable part 1 in a moving body such as an airplane or a vehicle that is mounted with an antenna. The movable part 1 is provided with an antenna 3 for microwave communication with a communication satellite, a ground base station, or the like, an EL motor 4 for rotating the antenna 3 about the EL (elevation) axis, and an AZ motor 5 for rotating the antenna 3 about the AZ (azimuth) axis. The movable part 1 is also provided with an EL angle detector 6 for detecting the EL angle of the antenna 3, an AZ angle detector 7 for detecting the AZ angle of the antenna 3, and an antenna control section 8 for controlling the EL motor 4, the AZ motor 5, the EL angle detector 6, and the AZ angle detector 7. The antenna control section 8 is provided with a drive control section 9 for driving the EL motor 4 and the AZ motor 5 and a position detecting section 10 for reading antenna angles detected by the EL angle detector 6 and the AZ angle detector 7 and for outputting the antenna angles thus read to the drive control section 9.
In the fixed part 2, reference numeral 11 denotes a transceiver for generating a radio signal to be output from the antenna 3 and for frequency-converting a reception signal that is supplied from the antenna 3 and performing signal processing on a resulting signal. Reference numeral 12 denotes an attitude information detecting section for detecting the attitude of the moving body such as an airplane or a vehicle that is mounted with the antenna 3. For example, the attitude detecting section 12 detects attitudes of the moving body about the roll axis, the yawing axis, and the pitch axis and a latitude and longitude. Reference numeral 13 denotes a drive instruction generating section for converting attitude information obtained by the attitude detecting section 12 into information suitable for a coordinate system that is employed in the antenna control section 8 and for generating a drive instruction for a motor drive control. Reference numeral 14 denotes an AC power source of the movable part 1 and the fixed part 2, and reference numeral 15 denotes an AC/DC converter for converting an AC output of the AC power source 14 into DC power.
Reference numeral 16 denotes a waveguide rotary coupler that is provided between the movable part 1 and the fixed part 2 to transmit a radio output signal from the transceiver 11 to the antenna 3 and to transmit a reception signal from the antenna 3 to the transceiver 11. Reference numeral 17 denotes a slip ring that is provided between the movable part 1 and the fixed part 2 to transmit a drive instruction signal from the drive instruction generating section 13 to the drive control section 9. Reference numeral 18 denotes a slip ring that is provided between the movable part 1 and the fixed part 2 to transmit DC power produced by the AC/DC converter 15 to the antenna control section 8.
The operation of the above conventional antenna apparatus will be described below. The directivity of an antenna that is mounted on a moving body varies depending on the attitude of the moving body. The conventional antenna apparatus of FIG. 10 has the EL motor 4 and the AZ motor 5 for driving the antenna 3 about the EL axis and the AZ axis, respectively. A result of driving of the antenna 3 by the motors 4 and 5 is detected as antenna angles by the EL angle detector 6 and the AZ angle detector 7, read by the position detector 10, and then input to the drive control section 9. On the other hand, latitude/longitude information and attitude information of the moving body are obtained by the attitude detecting section 12. In many cases, as in this antenna apparatus, the attitude information of a moving body is represented by a roll coordinate, a pitch coordinate, and a yawing coordinate. The attitude information of the moving body concerned is coordinate-converted by the drive instruction generating section 13 into information suitable for the EL/AZ coordinate system that is employed in the drive control section 9, and the converted information is output to the drive control section 9 as a drive instruction. The drive control section 9 calculates a direction to which the antenna 3 should be directed based on the latitude/longitude information of the moving body and position information of a counterpart station such as a communication satellite, and drives the EL motor 4 and the AZ motor 5 after compensating the calculated direction for the attitude information of the moving body, that is, angular variations of the antenna 3 that are caused by a variation in its attitude.
For exchange of signals between the movable part 1 and the fixed part 2, the conventional antenna apparatus uses transmission parts such as the waveguide rotary coupler 16 and the slip rings 17 and 18. It is necessary to transmit a radio signal from the transceiver 11 to the antenna 3 and to transmit a reception signal from the antenna 3 to the transceiver 11. For transmission of a radio signal, a waveguide, which is high in transmission efficiency, may be used depending on the frequency band. In this antenna apparatus, the waveguide rotary coupler 16 is used between the movable part 1 and the fixed part 2. The waveguide rotary coupler 16, which is a waveguide coupler capable of rotation about a single axis, is disposed on the AZ axis as usual. That is, the movable part 1 is supported by the fixed part 2 in such a manner as to be able to rotate about the AZ axis and the waveguide rotary coupler 16 is disposed on the AZ axis. The slip rings 17 and 18 for transmitting attitude information and power, respectively, is disposed between the movable part 1 and the fixed part 2 on the same axis (i.e., the AZ axis) as the waveguide rotary coupler 16 is. The waveguide rotary coupler 16 and the slip rings 17 and 18 can transmit a radio output signal, attitude information, and power, respectively.
Although in the configuration of FIG. 10 the AZ motor 5 and the AZ angle detector 7 are provided in the movable part 1, they may be provided in the fixed part 2. In the latter case, the AZ motor 5 that is provided in the fixed part 2 rotates the movable part 1 about the AZ axis. Also in this case, it is necessary to transmit a radio output signal, attitude information, and power from the fixed part 2 to the movable part 1 via the waveguide rotary coupler 16 and the slip rings 17 and 18, respectively, that are disposed on the AZ axis.
The conventional antenna apparatus is configured in such a manner as to use the slip rings 17 and 18 to transmit attitude information and power, respectively, from the fixed part 2 to the movable part 1. Each of the slip rings 17 and 18 has a structure that a brush that is provided on a rotary shaft of one of the fixed side and the movable side is in contact with a ring-like electrode that is provided on a rotary shaft of the other, and hence is an electric part in which abrasion occurs between the brush and the ring-like electrode. Whereas communication equipment to be used in airplanes, ships, etc. are in many cases required to be highly reliably, the conventional antenna apparatus has a problem that the slip rings 17 and 18 used therein lower the reliability. That is, the slip rings 17 and 18 are a factor of causing such a failure as impairs signal transmission, because abrasion or dew condensation may occur there. To remove such a failure-causing factor, it is necessary to increase the mechanical accuracy and the rigidity of mechanical parts that incorporate the brush and the ring-like electrode as well as to take proper measures relating to a heat-related environment. There is another problem that mechanical parts for transmitting a radio signal, power, and attitude information need to be provided on the AZ axis along which the movable part 1 and the fixed part 2 are coupled to each other and it is difficult to miniaturize those parts.
The present invention has been made solve the above problems in the art, and an object of the invention is therefore to provide an antenna apparatus and a waveguide rotary coupler that enable signal transmission between the movable part and the fixed part in a non-contact manner and that can miniaturize the structures on the AZ axis.
A first aspect of the invention provides an antenna apparatus which performs microwave communication in such a manner that a radio signal generated by a transceiver that is provided in a fixed part is supplied to an antenna that is provided in a movable part and the antenna is drive-controlled, comprising a drive control section provided in the movable part, for drive-controlling a motor for rotating the antenna; a waveguide rotary coupling device for transmitting a radio signal from the transceiver to the antenna; a primary coil provided in the fixed part; and a secondary coil provided provided in the movable part, for supplying the drive control section with electromotive force that is inducted in itself by a current flowing through the primary coil.
The antenna apparatus according to the first aspect of the invention may be such that the primary coil provided on a member, in the fixed part, of the waveguide rotary coupling device; and the secondary coil provided on a member, in the movable part, of the waveguide rotary coupling device.
The antenna apparatus according to the first aspect of the invention may be such that the primary coil provided on a member in the fixed part so as to be located outside a side surface of the waveguide rotary coupling device with a rotary axis of the waveguide rotary coupling device as a center; and the secondary coil provided on a member in the movable so as to be opposed to the primary coil outside a side surface of the waveguide rotary coupling device.
The antenna apparatus according to the first aspect of the invention may be such that the primary coil and the secondary coil respectively provided two sets of coil for power transmission system and signal transmission system.
The antenna apparatus according to the first aspect of the invention may be such that the drive control section drive-controls a motor for rotating the antenna about an elevation rotation axis, and wherein a motor for rotating the movable part about an azimuth rotation axis of the antenna is provided in the fixed part.
The antenna apparatus according to the first aspect of the invention may be such that a signal obtained by super imposing a drive instruction signal on an AC power-supply current is input from a power system in the fixed part to the primary coil, and in the movable part the AC power-supply current and the drive instruction signal are separated from electromotive force induced in the secondary coil.
The antenna apparatus according to the first aspect of the invention may be such that an infrared transmitting section provided in the fixed part, for sending a drive instruction signal in the form of infrared light; and an infrared receiving section provided in the movable part, for receiving the drive instruction signal sent from the infrared transmitting section and for outputting the received drive instruction signal to the drive control section.
The antenna apparatus according to the first aspect of the invention may be such that the infrared transmitting section sends the infrared light toward an inside surface of a radome that covers the antenna, and the infrared receiving section receives infrared light that is reflected by the inside surface of the radome.
A second aspect of the invention provides a waveguide rotary coupler comprising a first waveguide member having a first waveguide that is circular in cross-section; a second waveguide member having a second waveguide having approximately the same cross-section as the first waveguide, an end face of the second waveguide member being opposed to an end face of the first waveguide member; a rotary bearing that couples the first waveguide member and the second waveguide member in such a manner that they are rotatable about a central axis of the first and the second waveguides; a first coil holder that is provided on the first waveguide member in a ring-like manner with the central axis of the first and second waveguides as a center and that holds a first coil; and a second coil holder that is provided on the second waveguide member in a ring-like manner with the central axis of the first and second waveguides as a center, and that holds a second coil that is opposed to the first coil, wherein the first and second coil holders are so shaped as to surround the first and second coils in a cross-section that is obtained by cutting the first and second coil holders by a plane including the central axis of the first and second waveguides.
In the waveguide rotary coupler according to the second aspect of the invention, wherein the first and second coil holders are formed separately from the first and second wave guide members, respectively, and then connected to the first and second waveguide members, respectively, after the first and second waveguide members are coupled to each other by the rotary bearing.
In the waveguide rotary coupler according to the second aspect of the invention, wherein the second coil is located outside the first coil and coextend with the first coil around the central axis of the first and second waveguides.
The waveguide rotary coupler just described above may be such that the first coil holder holds two first coils and the second coil holder holds two second coils that are opposed to the respective first coils.
In the waveguide rotary coupler according to the second aspect of the invention, the first and second waveguide members may be made of a magnetic material.
In the waveguide rotary coupler according to the second aspect of the invention, the rotary bearing may be made of a ceramic material.
According to the invention, in the antenna apparatus, power and a drive instruction signal can be transmitted, in a non-contact manner, from the fixed part to the drive control section that is provided in the movable part. Therefore, the factors that may cause failures in the case of using slip rings can be eliminated and the mechanical structures provided on the AZ axis between the fixed part and the movable part can be reduced in size.
Further, according to the invention, since the waveguide rotary coupler is provided with a transformer having coils that are coupled to each other electromagnetically, not only a radio signal but also power and a drive instruction signal can be transmitted in a non-contact manner.